A stock's price is $100 at the beginning of a year. There is a 25 percent chance that the price will be $90 at the end of the year, and a 75 percent chance that the price will be $130 at the end of the year. The stock will pay a dividend of $10 during the year.
Calculate the standard deviation of the stock's return. Enter the number as a percentage without a '%' sign and round to two decimal places?